[LVI][ValueTracking] Take UB-implying attributes into account in `isSafeToSpeculativelyExecute` (#137604)

Closes https://github.com/llvm/llvm-project/issues/137582.

In the original case, LVI uses the edge information in `%entry ->
%if.end` to get a more precise result. However, since the call to `smin`
has an `noundef` return attribute, an immediate UB will be triggered
after optimization.

Currently, `isSafeToSpeculativelyExecuteWithOpcode(%min)` returns true
because
https://github.com/llvm/llvm-project/commit/6a288c1e32351d4be3b7630841af078fa1c3bb8b
only checks whether the function is speculatable. However, it is not
enough in this case.

This patch takes UB-implying attributes into account if
`IgnoreUBImplyingAttrs` is set to false. If it is set to true, the
caller is responsible for correctly propagating UB-implying attributes.

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index e49e004..2a56248 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -1701,7 +1701,8 @@ ValueLatticeElement LazyValueInfoImpl::getValueAtUse(const Use &U) {
     // of a cycle, we might end up reasoning about values from different cycle
     // iterations (PR60629).
     if (!CurrI->hasOneUse() ||
-        !isSafeToSpeculativelyExecuteWithVariableReplaced(CurrI))
+        !isSafeToSpeculativelyExecuteWithVariableReplaced(
+            CurrI, /*IgnoreUBImplyingAttrs=*/false))
       break;
     CurrU = &*CurrI->use_begin();
   }